As the flush mount wake fins are today standard, we have the chance to try different size & shape fins relative easily.
I have found that fins do a BIG difference on how a board ride. So this thread is for sharing our experiences looking for the best setup for our boards.

it is not only the size and shape of a fin, but also the position.
You can have more grip if you move the fins more to the end of the board, and if you like it looser more to the middle.
That is why we have the VFS (vario fin system) so you can have different grips with the same fins, just for what you prefer.

After testing many fins and shapes we found out that our boards (144 and 155)run best with 1.8 or 2.0 fins. This size will give you rfect grip in turns and overpowered situations but the board will be still loose for switching.

All I know is that fins make things way easier. I have a really nice custom twintip. It was my first board and I got it knowing it was going to be difficult to learn on. I bought it when finless was fashionable. It had one wake fin in the center of each tip, and that's it. I _really_ struggled with that board. Then I took a lesson and borrowed a board with lots of fins. I was up and going almost right away. The fins made a huge difference. I went back to my own board and was struggling again. I finally took the board back, and the manufacturer added some fins (all their new boards have lots of fins). I've only ridden it for a few very-underpowered runs, but I can easily tell the new fins have made a huge difference.
I know there are some good kiteboarders who go finless (Hung Vu is a big proponent), but for me (and I'd think other learners), fins are a big advantage.
Cheers,
AL

when you ride _really_ overpowered with a wakeboard (only centerfins), you sometimes get the point when you loose your grip in slow-motion. your edge just drifts out of the water very slowly and there's nothing you can do (i mean really overpowered, where edging harder is just impossible).

in this moment, you know that just one little fin in the end of your board would be a great help - there's not much to do for that fin, just a little tiny bit more grip would be enough to keep the board edging ....

I have found that on boards with a really straight outline one fin on each end is all you need to edge well because the piece of rail sticking out on the tail acts like another fin. This kind of design rides loose, edges well and is really easy to flip to switch stance. The naish hazmat is maybe an example, although I have not ridden one myself.

The downside of the straight outline is that it does not turn as fast, such as for riding waves.